1. Field of Invention
This invention is in the field of low molecular weight olefin copolymers; more particularly, this invention relates to the salts, i.e., ionomers, of low molecular weight copolymers of an .alpha.-olefin and an unsaturated carboxylic acid, preferably an .alpha.,.beta.-ethylenically unsaturated carboxylic acid having up to 100 percent of the carboxylic acid groups reacted with at least one amino acid. The ionomer is useful for flushing pigments.
2. Description of Related Art
The process of flushing pigments is reviewed in Great Britain Patent No. 915,453, and by Apps, Printing Ink Technology, Chemical Publishing Co., Inc., N.Y., pp.498-500 (1959). Flushing is a process to prepare pigment dispersions in which the pigments remain finely divided and in a suitable form for further processing such as incorporation into polymeric compositions and inks.
During the manufacture of pigments an aqueous mass of pigment is produced. The removal of all of the water can result in the pigments agglomerating. Some of the water is removed leaving the finely divided pigment as a wet cake. The aqueous mass of pigment is mixed with a polyolefin usually of low molecular weight. The mixture is coagulated and the aqueous phase is removed, typically by heating the composition, optionally in a vacuum. The pigment is dispersed in the low molecular weight polymer which can optionally be pulverized.
Low molecular weight polyethylene waxes are used to flush pigments. The flushed pigments are useful in polymeric compositions used for fibers, molding compounds, extrusion compounds, sheets, film, and the like. Flushed pigments have been used in compositions based on polyethylene, polyvinylchloride, ABS, polyamides, and polycarbonates, among other.
Low molecular weight olefinic copolymers, particularly low molecular weight ethylene copolymers, are described in U.S. Pat. No. 3,658,741. This patent discloses homogeneous copolymers of ethylene and various comonomers including unsaturated acids and their derivatives, such as esters and amides. Examples of the derivatives include methyl acrylate, methyl methacrylate, ethyl acrylate, and dimethylaminoethyl methacrylate.
U.S. Pat. No. 4,381,378 discloses a method for the preparation of low molecular weight copolymer salts from low molecular weight copolymer acids of .alpha.-olefins and .alpha.,.beta.-ethylenically unsaturated carboxylic acids. Preferred copolymers are copolymers of ethylene and acrylic acid.
U.S. Pat. Nos. 4,412,040 and 4,603,172 disclose low molecular weight copolymer salts for use as lubricants and dispersion aides in plastics. The disclosed salts include salts of low molecular weight copolymers of .alpha.-olefins and .alpha.,.beta.-ethylenically unsaturated carboxylic acids. Preferred copolymers are copolymers of ethylene and acrylic acid.
U.S. Pat. Nos. 3,388,186 and 3,465,059 disclose polyamide compositions. The compositions are made by grafting amino acids or lactams onto a backbone chain containing recurring ethylenic units and reactive sites, such as carboxyl radicals of acid, ester or salt groups, and particularly acrylic acid esters. The proportion of the copolymer backbone to the polyamide graft can vary between 2 and 90 percent. The copolymers disclosed for use as part of the backbone chain have a number average molecular weight of at least about 13,700 in U.S. Pat. No. 3,388,196; and at least 10,000 in U.S. Pat. No. 3,465,059.
U.S. Pat. No. 3,634,543 discloses nucleated graft polymers of polycaprolactam on carboxy containing copolymeric backbone. The graft polymer is prepared by polymerization of caprolactam in the presence of a copolymer of an olefin and an unsaturated carboxylic acid.
U.S. Pat. No. 4,035,438 discloses an impact resistant mixture of polyethylene; a graft polymer of an ethylene/acrylic acid copolymer or ethylene/methacrylic acid copolymer as a graft substrate and grafted polymerized units of .epsilon.-caprolactam; and polycaprolactam. The copolymers for use as graft substrates are those which contain 1 to 10 mol percent of (meth)acrylic acid, preferably from 30 percent to 70 percent in the form of the sodium salt.